First of all, what do you understand by "really big enlargements"? 8x10? If you take perfectly framed pictures every time you press the shutter release, then you can buy 3MP if you wish. I am not so perfect. I always end up changing the framing in postprocessing. Sometimes I end up with just a fragment of the original photo.
My advice is, get whatever you can afford, it will not go to waste. These days when 5MP costs almost the same as 3MP, why would you penny-pinch yourself into a situation where you may lose some good shots?
As to the shutter delay, the most expensive cameras don't have it. It will take a while before consumer gear is at the same level. And yes, www.dpreview.com
does mention delay in their reviews.